Ignition Coil: Description and Operation

The Ignition Coil uses the principle of mutual induction to step up battery voltage to the high voltage necessary for ignition. The Ignition Coil contains two windings of copper wire around a soft iron core. The primary winding is made of a hundred or so turns of a heavy gage wire. It is connected to the battery (through the ignition switch) so that current flows through it, thus creating a magnetic field. When current flow in the primary winding is interrupted (by the the igniter in the distributor interrupting circuit ground), the sudden collapse of the magnetic field induces a high voltage in the secondary windings. The ratio of turns in the primary windings to the number of turns in the secondary windings determines the increase in voltage.